Our studies in the urinary excretion of nonesterified cholesterol (NEC) in the normal and abnormal individual have shown that this urinary steroid is evaluated in patients with carcinomas of the steroid- producing glands and their main target organs. In contrast, patients with nonmalignant or malignant neoplasms other than the aforementioned ones, have revealed a normal urinary excretion of NEC. In addition, our studies have also shown that the NEC excretion correlates with the clinical course of the disease in patients receiving treatment, mainly radiation therapy and/or surgery. This test, therefore, appears to have prognostic value. Such evidence encourages the extension of our investigations to encompass a survey of the NEC excretion in (a) Patients with preclinical evidence of malignancy as indicated by Papanicolaou stain; (b) Patients with histologically proven neoplasms of the steroid-related organs; (c) Patients with carcinomas of steroid- related organs who are receiving therapy, and (d) Patients with histologically proven neoplasms of nonsteroid-association. In order to accumulate sufficient cases and experimental evidence to provide a meaningful clinical and statistical correlation, the studies should be performed in accordance with the time periods recommended for the clinical evaluation of survival on these neoplastic diseases. Correlation of such data will show if the NEC determinations can be used as a biochemical diagnostic aid, as a screening test, and as a nonsubjective method to monitor therapy in patients with carcinomas of the steroid-producing glands and their target organs.